NVDA with Firefox only works when the img role is applied to <svg>
that are not implemented inline, at least preliminary testing
indicates that.

This does not work on regular html elements, since id attributes must
be unique within the page.
But doesn't <svg> work a bit like <iframe> elements in that they are
basically a totally separate entity from the rest of the page?

In that case I could use aria-labelledby="the same id" on all the
<svg> elements.
I am no svg expert yet (that is obvious *grin*) but I am dabbling in
it and thrilled by the possibilities for making images a lot more
ccessible.